Proposal for Joint EIT-MDI observations/analysis from SOHO
Werner Neupert

Title:   Correlation of Coronal Loop Evolution with
Photospheric Magnetic Fields

Keywords:  Coronal loops,  coronal heating

Proposal:  We propose to study the evolution of active
region coronal loops as it may relate to changes in the
underlying photospheric magnetic field.  These comparisons
will be made by comparing a sequence of  EIT sub-field
(probably 7x7 arc min) images with a corresponding sequence
of the photospheric B field obtained by the MDI instrument.
Such a comparison is intended to investigate whether the
appearance of coronal loops and their subsequent development
over time, such as evolution of density and temperature
 and the degree of shear relative to the photospheric
neutral line, can be related to the evolution of the
underlying photospheric field and, specifically,to motions
of the photospheric footpoints of the coronal features.  In
addition to direct comparison of data sets, the MDI data can
also be used to calculate potential or force-free coronal
fields, with the results being compared with EIT images.
Results of this study will be important in evaluating
Parker's theory that the twisting together of coronal loops
due to footpoint motions can lead to nanoflares and
subsequent coronal heating.   The observational program will
require intermittent tracking of several active regions over
a period of days, with concurrent MDI data, so that the
evolution of the corona in response to field changes can be
documented.

Specific: Tasks:

EIT images should be taken at all four wavelengths:  the
three coronal wavelengths will be used to follow the
evolution of  particular coronal features while the 304 A
image will be used to match the EIT data spatially with MDI
observations. Each set of EIT observations should include at
least one image at 304 A
EIT image size should be 5x5 blocks (7x7 arc min).  The
regions to be selected should initially be on the east
(solar) side of MDI's high resolution field so that they can
be tracked by both instruments over a period of several
days.

EIT observations should be taken at a sufficiently rapid
cadence so that coronal changes can be unambiguously
followed.  Clearly, that depends on the rate at which a
region is evolving.  As a start, observations interleaved
with the LASCO synoptic program, i.e., some observations
every one and a half hours, would be acceptable.   The
program could be run for an entire week during which several
regions would be observed.  Selection of regions would be
based on full-Sun EIT images and would be made several days
in advance.

EIT Consortium Collaborators:  TBD

External Collaborator:  Ted Tarbell and other MDI
experimenters TBD

EIT Consortium Member: Yes